A lesion site generally has a different color from normal mucosal tissue. Through improvements in the capabilities of color endoscope apparatuses, it has also become possible to also identify lesion sites that have a slight difference in color from normal tissue. However, an operator needs to receive extensive training under an experienced operator in order to be able to accurately identify normal tissue and a lesion site based on a slight color difference in an endoscopic image. Also, it is not easy for even an experienced operator to identify a lesion site based on a slight color difference, and such identification has required careful work. In view of this, in order to make the identification of lesion sites and the like easier, Patent Document 1 for example proposes an electronic endoscope system that includes a function for performing color conversion processing for emphasizing color differences in endoscope image data that was obtained using white light.